Dear Miss Snark,
Let’s say I’m a writer and you’re an agent. In the post James Frey era of candor, which would you rather I be, the forty-something author of a first novel, or the fifty something author of three previous hardly selling YA novels (as well as seven other books of non-fiction).
Or, forgetting the age thing, as if you could, is it easier to sell the first novel of an unknown or the 11th book of a mid-to-bottom of the list journeyman (assuming it's the same book).
Well, I am an agent, and I'm pretty sure you ARE a writer so let's leave off the hypotheticals. None of these questions matter because no matter what I want, you are who you are, and your work is something I want to represent or it isn't.
What you are asking about is packaging, and any agent worth his/her salt can change packaging six days a week and twice on Sundays.
YOUR job is to write the best book you can and find an agent with a salt shaker.